HIF1A and neoplasm: For example, hypoxia leads to the significant upregulation of PD‐L1 on splenic MDSCs in tumor‐bearing mice, and this upregulation depends on hypoxia‐inducible factor‐1α (HIF‐1α), which regulates PD‐L1 expression by directly binding to the transcriptionally active hypoxia‐responsive element in the proximal promoter of PD‐L1 [104, 105].